Those Are Greenbugs...

Published: May 1, 2011

Dead patches of cool-season grasses, such as Kentucky bluegrass and tall fescue, have been reported around the central Missouri region in the past several weeks. While greenbugs exist every year, this is the first reported cases in over 20 years. Greenbugs will also feed on annual bluegrass and chewings fescue. Close inspection of the damaged areas will reveal clusters of green aphids lined up on leaf blades.

The greenbug is an aphid or sometimes referred to as a "plant louse." They have a piercing, sucking mouth-part that removes sap from turfgrasses. When feeding, they inject saliva that is toxic to plant tissue causing the tissue around the feeding site to die. Damaged begins as chlorotic (yellowing) lesions that eventually turn brown. With the loss of sap and the translocation of toxins throughout the plant, the whole plant, including roots, will die. Heavy infestations can amount to 2000 to 3000 aphids per square foot. If left untreated, damaged sites will require re-seeding or re-sodding.

Greenbugs seem to favor heavily fertilize turfgrasses in shaded areas; however, damage has been seen in just the opposite – open areas under low fertility. Damage may also occur along foundation walls, fences or other upright structures. As infestations spread, the highest numbers of greenbugs will be noticed in the green grass on the perimeter of damaged patches.

Greenbugs can become windborne and move to new sites. They can also be carried on grass clippings attached to mowers or boots, in bagged clippings, or on infested sod. Lawn care operators should be particularly careful not to transport greenbugs from infested sites to non-infested sites.

Management:

In most years, greenbug populations are easily controlled by natural predators, such as lady beetle larvae, lacewings, and tiny parasitic wasp. When infestations are high, large numbers of these predators may be observed.

Endophyte-infested varieties of tall fescue, fine-leafed fescue, or perennial ryegrass are resistant to greenbugs. Consider over-seeding damaged areas with one of these turfgrass species with endophyte.

Insecticides may be the only solution in heavily infested areas. If damage is localized, spot treatments may be adequate; however, treat up to 6 feet beyond the damaged area. Liquid formulations of insecticides work best; granular formulations are less effective. Treated areas should not be irrigated or mowed within 24 hours. The goal is to leave residues of insecticides on the leaf blade. Rainfall, soon after an application, may reduce the effectiveness of the insecticide. Areas should be inspected for greenbugs and retreatment may be necessary.

Greenbugs are fairly easy to control with contact and systemic insecticides; however, multiple applications may be required for complete control. Several products are available for lawns (commercial and residential) and are listed below. Note that some products (Acephate, Orthene, etc.) are labeled for golf course and sod farms only and Orthene does not have a landscape label. Other insecticides are labeled for control of aphids on lawns and in general on landscape ornamentals. Keep in mind that many of the products listed below need to be applied by a licensed applicator since several of these products are restricted use pesticides. Products like Sevin and Merit can be purchased over-the-counter for homeowner use. Always read the product label before purchasing and prior to use.